Device for compensating for a mismatch of a transmitter and a method of compensating for the mismatch

ABSTRACT

A device for compensating for a mismatch of a transmitter and a method of compensating for the mismatch is provided. The device for compensating for a mismatch of an up-converter in a direct conversion transmitter, comprises: a mismatch compensating unit for compensating for an input signal using a first mismatch compensation value to generate a mismatch compensation signal; a down-converter for down-converting a radio frequency (RF) signal to generate an intermediate frequency (IF) signal, the RF signal being generated by up-converting the mismatch compensation signal; a square unit for squaring the IF signal; and a controller for calibrating the first mismatch compensation value to determine a second mismatch compensation value such that a direct current (DC) component of the squared IF signal has a minimum value to compensate for the mismatch of the up-converter using the second mismatch compensation value.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No.2003-49030 filed on Jul. 18, 2003, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a device for compensating for amismatch of a transmitter and a method of compensating for the mismatch,and more particularly, to a device and method for compensating for amismatch of a transmitter that occurs when up-converting a directconversion transmitter.

2. Discussion of the Related Art

In a communication device using heterodyne conversion, baseband signalsare converted to radio frequency (RF) signals, and vice versa via aplurality of stages of intermediate frequency (IF) signals. Thecommunication device using the heterodyne conversion utilizes a numberof RF components such as a SAW (Surface Acoustic Wave) filter and an IFamplifier to reduce the cost and weight of the communication device.

In the communication device using direct conversion, baseband signalsare converted to RF signals, and vice versa in a single step without anRF to IF conversion step. Thus, in such a communication device, forexample, a mobile phone, the mobile phone's receiver or transmitter maybe implemented using a small number of components or in a single chip.In addition, leaked local oscillation signals may be mixed betweenclosely spaced circuit components, and high direct current (DC) offsetlevels may exist due to a mismatch of the transmitter or the receiver insuch communication devices.

As a DC offset cancellation circuit for a direct conversion receiver hasbeen disclosed in Korean Laid-Open Patent Publication No. 2003-0034472,there still exists a need for a DC offset cancellation circuit for usewith a direct conversion transmitter.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a device forestimating a mismatch of a transmitter comprising an up-convertercomprises: a mismatch compensating unit for receiving a first in-phasesignal and a first quadrature-phase signal to generate a mismatchcompensation signal using a mismatch compensation value; adown-converter for mixing a radio frequency (RF) signal with anoscillating signal to generate a second in-phase signal and a secondquadrature-phase signal, wherein an up-converter generates the RF signalusing the mismatch compensation signal; a first square unit for squaringthe second in-phase signal; a second square unit for squaring the secondquadrature-phase signal; a first adder for adding an output of the firstsquare unit to an output of the second square unit; and a low passfilter for filtering an output of the first adder to generate anestimated mismatch value, wherein the mismatch compensation value isused to minimize the estimated mismatch value. The up-converter may be adirect up-converter.

The down-converter comprises a first local oscillator for generating afirst oscillating signal; a first mixer for mixing the RF signal withthe first oscillating signal to generate an intermediate frequency (IF)signal; a second low pass filter for filtering an output of the firstmixer; a second local oscillator for generating a second oscillatingsignal; and a second mixer for mixing an output of the second low passfilter with the second oscillating signal to generate a second in-phasesignal and a second quadrature-phase signal.

According to another aspect of the present invention, a method ofcompensating for a mismatch of a transmitter having a directup-converter comprises: adjusting a phase and a gain of a first in-phasesignal and a first quadrature-phase signal using a first mismatchcompensation value to generate a mismatch compensation signal;up-converting the mismatch compensation signal to generate an RF signal;down-converting the RF signal to generate a second in-phase signal and asecond quadrature-phase signal; squaring the second in-phase signal andthe second quadrature-phase signal, to add the squared second in-phasesignal to the squared second quadrature-phase signal, and to generate anestimated mismatch value; and generating a second mismatch compensationvalue that is determined such that the estimated mismatch value has aminimum value to compensate for the mismatch of the transmitter usingthe second mismatch compensation value.

According to yet another aspect of the present invention, a method ofcompensating for a mismatch of an up-converter comprises: compensatingfor an input signal using a first mismatch compensation value togenerate a mismatch compensation signal; up-converting the mismatchcompensation signal to generate an RF signal; down-converting the RFsignal to generate an IF signal; squaring the IF signal; and repeatingthe above steps by changing the first mismatch compensation value todetermine a second mismatch compensation value such that a directcurrent (DC) component of the squared IF signal has a minimum value, andto compensate for the mismatch of the up-converter using the secondmismatch compensation value.

The first mismatch compensation value comprises a phase value or a gainvalue. The input signal comprises a first in-phase signal and a firstquadrature-phase signal. Generating the mismatch compensation signalalso comprises shifting a phase value of the first quadrature-phasesignal based on a phase value of the first mismatch compensation valueto generate a third quadrature-phase signal having a lead phase withrespect to the first quadrature-phase signal; shifting the phase of thefirst quadrature-phase signal based on the phase value of the firstmismatch compensation value to generate a fourth quadrature-phase signalhaving a delay phase with respect to the first quadrature-phase signal;adding the first in-phase signal to the third quadrature-phase signal togenerate a first mismatch compensation signal; and obtaining adifference between the first in-phase signal and the fourthquadrature-phase signal to generate a second mismatch compensationsignal. Generating the mismatch compensation signal further comprisesamplifying the second mismatch compensation signal using the gain valueof the first mismatch compensation value.

According to yet another aspect of the present invention, a device forcompensating for a mismatch of an up-converter comprises: a mismatchcompensating unit for compensating for an input signal using a firstmismatch compensation value to generate a mismatch compensation signal;a down-converter for down-converting an RF signal to generate an IFsignal, the RF signal being generated by up-converting the mismatchcompensation signal; a square unit for squaring the IF signal; and acontroller for calibrating the first mismatch compensation value todetermine a second mismatch compensation value such that a DC componentof the squared IF signal has a minimum value in order to compensate forthe mismatch of the up-converter using the second mismatch compensationvalue.

The input signal comprises a first in-phase signal and a firstquadrature-phase signal. The mismatch compensating unit furthercomprises: a first phase shifter for shifting a phase of the firstquadrature-phase signal based on the phase value of the first mismatchcompensation value to generate a third quadrature-phase signal having alead phase with respect to the first quadrature-phase signal; a secondphase shifter for shifting the phase of the first quadrature-phasesignal based on the phase value of the first mismatch compensation valueto generate a fourth quadrature-phase signal having a delay phase withrespect to the first quadrature-phase signal; a first adder for addingthe first in-phase signal to the third quadrature-phase signal togenerate a first mismatch compensation signal; and a subtractor forobtaining a difference between the first in-phase signal and the fourthquadrature-phase signal to generate a second mismatch compensationsignal.

The device further comprises an amplifier for amplifying the secondmismatch compensation signal using the gain value of the first mismatchcompensation value. The down-converter comprises: a first mixer formixing mix the RF signal with a first oscillating signal to generate afirst IF signal; a first low pass filter for filtering the first IFsignal; and a second mixer for mixing an output of the second low passfilter with a second oscillating signal to generate a pair of second IFsignals, the second IF signals being orthogonal each other. The squareunit comprises: a first square unit for squaring one of the second IFsignals; a second square unit for squaring one of the second IF signals;a second adder for adding an output of the first square unit to anoutput of the second square unit; and a second low pass filter forfiltering an output of the first adder to extract a DC component fromthe output of the first adder.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention will become more apparent bydescribing in detail exemplary embodiments thereof with reference to theaccompanying drawings, in which:

FIG. 1 illustrates an up-converter for estimating a mismatch of theup-converter according to an exemplary embodiment of the presentinvention;

FIG. 2 illustrates a mismatch compensating unit according to anotherexemplary embodiment of the present invention;

FIG. 3 is a block diagram showing a direct conversion transmitter havingthe mismatch compensating unit according to an exemplary embodiment ofthe present invention; and

FIG. 4 is a flowchart showing a method of estimating the mismatch of theup-converter according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 illustrates an up-converter for estimating a mismatch of theup-converter according to an exemplary embodiment of the presentinvention, FIG. 2 illustrates a mismatch compensating unit according toanother exemplary embodiment of the present invention, and FIG. 3 is ablock diagram showing a direct conversion transmitter having themismatch compensating unit according to an exemplary embodiment of thepresent invention.

Referring to FIG. 1, an up-converter 10 of a direct conversiontransmitter includes a mismatch compensation value inserting unit 20, amismatch estimating unit 30 and a compensating unit 49. The up-converter10 mixes baseband signals such as an in-phase (I) signal and aquadrature-phase (Q) signal with a local oscillating signal LO, andup-converts the baseband signals to a radio frequency (RF) signal. Amismatch of the up-converter 10 is estimated and the mismatch of theup-converter 10 is compensated based on an estimated mismatch value inorder to reduce signal distortion due to the mismatch of theup-converter 10.

A single tone baseband signal, into which a mismatch compensation value(or sweep variable) is inserted, is applied to the up-converter 10 viathe mismatch compensation value inserting unit 20. The up-converter 10mixes the local oscillating signal LO supplied from a local oscillatorwith mismatch compensation signals IF3_I(t) and IF3_Q(t) (shown in FIG.2) using a mixer, and up-converts the mixed result to generate an RFsignal RF(t) (shown in FIG. 3).

The mismatch estimating unit 30 down-converts the RF(t) signal, andestimates an estimated mismatch value such as a gain mismatch value anda phase mismatch value. The compensating unit 49 calibrates andcompensates for the mismatch of the up-converter 10 based on theestimated mismatch value.

As shown in FIG. 2, when the up-converter 10 receives the basebandsignals such as the in-phase (I) signal and the quadrature-phase (Q)signal, an adder 26 adds the in-phase (I) signal to a quadrature-phase(Q′) signal to provide the added signal to the up-converter 10, and asubtractor 28 obtains a difference between the in-phase (I) signal and aquadrature-phase (Q″) signal. An output of the subtractor 28 isamplified by an amplifier 29 (having a gain=1+ΔA2) and is provided tothe up-converter 10. In this case, the quadrature-phase (Q′) signal hasa lead phase with respect to the Q signal by φ_(ε2), and thequadrature-phase (Q″) signal has a delay phase with respect to the Qsignal by φ_(ε2). ΔA2 is a gain mismatch compensation value, and φ_(ε2)is a phase mismatch compensation value.

The up-converter 10 receives outputs from the adder 26 and thesubtractor 28, and mixes the outputs of the adder 26 and the subtractor28 with the local oscillating signal LO to generate the RF signal whosefrequency corresponds to the sum of the output signal of the adder 26(or the subtractor 28) and the local oscillating signal LO, or whosefrequency corresponds to the frequency difference between the outputsignal of the adder 26 (or the subtractor 28) and the local oscillatingsignal LO. The RF signal output from the up-converter 10 is passedthrough a band pass filter and an amplifier (not shown) and is radiatedfrom an antenna (not shown).

The RF signal output from the up-converter 10 is input to the mismatchestimating unit 30 to estimate the mismatch of the up-converter 10. Thecompensating unit 49 receives the estimated mismatch value andcompensates the mismatch of the up-converter 10 using the estimatedmismatch value.

Referring to FIG. 3, a direct conversion transmitter 100 is coupled to amismatch estimating & compensating unit 200. The mismatch estimating &compensating unit 200 includes a mismatch compensating unit 210, adown-converter 220, a square unit 230 and a control unit 240.

The mismatch compensating unit 210 includes an adder 212, a subtractor214, a first phase shifter 216, a second phase shifter 218 and anamplifier 219. The down-converter 220 includes first and second mixers221 and 224, first and second local oscillators 222 and 226, and a lowpass filter 223.

The controller 240 receives a direct current (DC) component from thesquare unit 230 and controls the first and second phase shifters 216 and218, the amplifier 219, and the local oscillator LO1 120 of the directconversion transmitter 100.

The first mixer 221 of the down-converter 220 mixes a local oscillatingsignal ω_(L03) with the RF signal output from the transmitter 100 togenerate an IF signal IF4(t). The low pass filter 223 removesunnecessary high frequency signals from the output signals of the firstmixer 221. The second mixer 224 mixes a local oscillating signal ω_(L04)with the low pass filtered signal output from the low pass filter 223 togenerate IF signals IF2(t) such as an in-phase (I) signal IF2_I(t) 227and an quadrature-phase (Q) signal IF2_Q(t) 228.

A first square unit 232 squares the in-phase (I) signal IF2_I(t) 227,and a second square unit 234 squares the quadrature-phase (Q) signalIF2_Q(t) 228. An adder 236 adds an output of the first square unit 232to an output of the second square unit 234. A low pass filter 238 lowpass filters an output of the adder 236 to extract a DC component fromthe output of the adder 236, and provides the extracted DC component tothe controller 240.

The in-phase (I) signal and quadrature-phase (Q) signal input to thedirect conversion transmitter 100 are defined as Equation 1.I(t)=cos(ω_(IF3) t), Q(t)=sin(ω_(IF3) t)  Equation 1

When the in-phase (I) signal and quadrature-phase (Q) signal are treatedwith the gain mismatch compensation value ΔA2 and the phase mismatchcompensation value φ_(ε2), the mismatch compensation signals IF3_I(t)and IF3_Q(t) are defined as Equation 2. $\begin{matrix}\begin{matrix}{{{IF3\_ I}(t)} = {\frac{1}{2}\left\lbrack {{\cos\left( {\omega_{IF3}t} \right)} + {\sin\left( {{\omega_{IF3}t} + \phi_{ɛ2}} \right)}} \right\rbrack}} \\{{{IF3\_ Q}(t)} = {{\frac{1}{2}\left\lbrack {{\sin\left( {{\omega_{IF3}t} - \phi_{ɛ2}} \right)} - {\cos\left( {\omega_{IF3}t} \right)}} \right\rbrack}\left( {1 + {\Delta\quad A_{2}}} \right)}}\end{matrix} & {{Equation}\quad 2}\end{matrix}$

When ω_(SP)=ω_(LO1)+ω_(IF3) and ω_(data)=ω_(LO1)−ω_(IF3), the RF signalRF(t) is defined as Equation 3. $\begin{matrix}\begin{matrix}{{{RF}(t)} = {{\frac{1}{4}{\left( {1 + {\Delta\quad A_{1}}} \right)\left\lbrack {{\cos\left( {\omega_{SP}t} \right)} + {\sin\left( {{\omega_{SP}t} + \phi_{ɛ2}} \right)}} \right\rbrack}} +}} \\{\frac{1}{4}{\left( {1 + {\Delta\quad A_{2}}} \right)\left\lbrack {{- {\cos\left( {{\omega_{SP}t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)}} -} \right.}} \\{\left. {\sin\left( {{\omega_{SP}t} + \phi_{ɛ2}} \right)} \right\rbrack +} \\{{\frac{1}{4}{\left( {1 + {\Delta\quad A_{1}}} \right)\left\lbrack {{\cos\left( {\omega_{data}t} \right)} - {\sin\left( {{\omega_{data}t} - \phi_{ɛ2}} \right)}} \right\rbrack}} +} \\{\frac{1}{4}{\left( {1 + {\Delta\quad A_{2}}} \right)\left\lbrack {{\cos\left( {{\omega_{data}t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)} -} \right.}} \\\left. {\sin\left( {{\omega_{SP}t} + \phi_{ɛ1}} \right)} \right\rbrack\end{matrix} & {{Equation}\quad 3}\end{matrix}$

As shown in Equation 3, ΔA1 is a gain mismatching value of thetransmitter 100, and φ_(ε1) is a phase mismatching value of thetransmitter 100.

Because a mixer of the up-converter 110 outputs the sum frequency(ω_(LO1)+ω_(IF3)) signal and the difference frequency (ω_(LO1)−ω_(IF3))signal, only the sum frequency (ω_(LO1)+ω_(IF3)) signal is selected by aband pass filter (not shown) and is provided to the down-converter 220as the RF signal.

The IF4(t) signal is defined as Equation 4 shown below. When the firstmixer 221 uses the local oscillating signal (ω_(LO3)), the mixer 221outputs a sum frequency (ω_(LO3)+ω_(SP)) sp) signal and a differencefrequency (ω_(LO3)−ω_(SP)) signal, and the low pass filter 223 selectsthe difference frequency (ω_(LO3)−ω_(SP)) signal. $\begin{matrix}\begin{matrix}{{{IF4}(t)} = {{\frac{1}{8}{\left( {1 + {\Delta\quad A_{1}}} \right)\left\lbrack {{\cos\left( {\omega_{IF4}t} \right)} + {\sin\left( {{\omega_{IF4}t} + \phi_{ɛ2}} \right)}} \right\rbrack}} +}} \\{\frac{1}{8}{\left( {1 + {\Delta\quad A_{2}}} \right)\left\lbrack {{- {\cos\left( {{\omega_{IF4}t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)}} -} \right.}} \\\left. {\sin\left( {{\omega_{IF4}t} + \phi_{ɛ1}} \right)} \right\rbrack\end{matrix} & {{Equation}\quad 4}\end{matrix}$

When the second mixer uses the local oscillating signal (ω_(LO4)) andwhen ω_(IF4)−ω_(LO4)=ω_(IF2)), the IF2_I(t) signal 227 and IF2_Q(t)signal 228 are defined as Equation 5. $\begin{matrix}\begin{matrix}\begin{matrix}{{{IF2\_ I}(t)} = {{\frac{1}{16}{\left( {1 + {\Delta\quad A_{1}}} \right)\left\lbrack {{\cos\left( {\omega_{IF2}t} \right)} + {\sin\left( {{\omega_{IF2}t} + \phi_{ɛ2}} \right)}} \right\rbrack}} +}} \\{\frac{1}{16}{\left( {1 + {\Delta\quad A_{2}}} \right)\left\lbrack {{- {\cos\left( {{\omega_{IF2}t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)}} -} \right.}} \\\left. {\sin\left( {{\omega_{IF2}t} + \phi_{ɛ1}} \right)} \right\rbrack\end{matrix} \\\begin{matrix}{{{IF2\_ Q}(t)} = {{\frac{1}{16}{\left( {1 + {\Delta\quad A_{1}}} \right)\left\lbrack {{\sin\left( {\omega_{IF2}t} \right)} + {\cos\left( {{\omega_{IF2}t} + \phi_{ɛ2}} \right)}} \right\rbrack}} +}} \\{\frac{1}{16}{\left( {1 + {\Delta\quad A_{2}}} \right)\left\lbrack {{- {\sin\left( {{\omega_{IF2}t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)}} -} \right.}} \\\left. {\cos\left( {{\omega_{IF2}t} + \phi_{ɛ1}} \right)} \right\rbrack\end{matrix}\end{matrix} & {{Equation}\quad 5}\end{matrix}$

The IF2_I(t) signal 227 and IF2_Q(t) signal 228 are squared by thesquare units 232 and 234, respectively, are added each other by theadder 236, is low pass filtered by the low pass filter 238, and theestimated mismatch value is defined as Equation 6. $\begin{matrix}\begin{matrix}{{{squaring}\left( {{IF2\_ I}^{2} + {IF2\_ Q}^{2}} \right)} =} \\{{\frac{1}{16^{2}}\begin{Bmatrix}\left\lbrack {{\left( {1 + {\Delta\quad A_{1}}} \right){\cos\left( {\Delta\quad\omega\quad t} \right)}} - \left( {1 + {\Delta\quad A_{2}}} \right)} \right. \\{\left. {\cos\left( {{\Delta\quad\omega\quad t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)} \right\rbrack +} \\\left\lbrack {{\left( {1 + {\Delta\quad A_{1}}} \right){\sin\left( {{\Delta\quad\omega\quad t} + \phi_{ɛ2}} \right)}} - {\left( {1 + {\Delta\quad A_{2}}} \right){\sin\left( {{\Delta\quad\omega\quad t} + \phi_{ɛ1}} \right)}}} \right\rbrack\end{Bmatrix}^{2}} +} \\{\frac{1}{16^{2}}\begin{Bmatrix}\left\lbrack {{\left( {1 + {\Delta\quad A_{1}}} \right){\sin\left( {\Delta\quad\omega\quad t} \right)}} - \left( {1 + {\Delta\quad A_{2}}} \right)} \right. \\{\left. {\sin\left( {{\Delta\quad\omega\quad t} + \phi_{ɛ1} - \phi_{ɛ2}} \right)} \right\rbrack +} \\\left\lbrack {{\left( {1 + {\Delta\quad A_{1}}} \right){\cos\left( {{\Delta\quad\omega\quad t} + \phi_{ɛ2}} \right)}} - {\left( {1 + {\Delta\quad A_{2}}} \right){\cos\left( {{\Delta\quad\omega\quad t} + \phi_{ɛ1}} \right)}}} \right\rbrack\end{Bmatrix}^{2}} \\{\equiv {\frac{1}{16^{2}}\left\lbrack {\left( {{\Delta\quad A_{1}} - {\Delta\quad A_{2}}} \right)^{2} + \left( {\phi_{ɛ1} - \phi_{ɛ2}} \right)^{2}} \right\rbrack}}\end{matrix} & {{Equation}\quad 6}\end{matrix}$

Equation 6 shows that the gain mismatching value ΔA1 of the transmitter100 and the phase mismatching value φ_(ε1) of the transmitter 100 may betracked using the mismatch compensation values such as the gain mismatchcompensation value ΔA2 and the phase mismatch compensation value φ_(ε2).

When ΔA2 and φ_(ε2) are set to satisfy the condition in which ΔA1=ΔA2and φ_(ε1)=φ_(ε2) so that the DC component of Equation 6 is minimized,the mismatch of the transmitter 100 is compensated. Therefore, thecontroller 240 changes the mismatch compensation values ΔA2 and φ_(ε2)to determine the final mismatch compensation values ΔA2′ and φ_(ε2)′that minimize the mismatch of the transmitter 100. The controller 240provides the final mismatch compensation values ΔA2′ and φ_(ε2)′ to thelocal oscillator LO1 120, the phase shifters 216 and 218, and theamplifier 219.

FIG. 4 is a flowchart showing a method of estimating the mismatch of theup-converter (e.g., 10 and 110 of FIGS. 1 and 3) according to anexemplary embodiment of the present invention. Referring to FIG. 4,mismatch compensation values ΔA2 and φ_(ε2) are generated (step S1), andthe mismatch compensation values ΔA2 and φ_(ε2) are incorporated with asingle tone input signals such an in-phase (I) signal and aquadrature-phase (Q) signal, and mismatch compensation signals IF3_I(t)and IF3_Q(t) are generated (step S2). The mismatch compensation signalsIF3_I(t) and IF3_Q(t) are up-converted into an RF signal by theup-converter 110 of FIG. 3 (step S3).

The RF signal is down-converted by the down-converter 220 of FIG. 3, andthe IF2_I(t) signal 227 and IF2_Q(t) signal 228 (both of FIG. 3) aregenerated (step S4). A DC component corresponding to the mismatch valueof the transmitter 100 is obtained using the IF2_I(t) signal 227 andIF2_Q(t) signal 228 (step S5). The DC component may be changed dependingupon the mismatch compensation values ΔA2 and φ_(ε2).

The estimated mismatch value is obtained when the mismatch compensationvalues ΔA2 and φ_(ε2) satisfy the condition in which the DC componenthas minimum value. It is determined if the mismatch compensation valuesΔA2 and φ_(ε2) satisfy the condition in which the DC component has aminimum value (step S6). When the DC component does not have the minimumvalue, steps S1-S5 are repeated. When the DC component has the minimumvalue, the mismatch compensation values ΔA2 and φ_(ε2) are set as theestimated mismatch value (step S7). The estimated mismatch value may bestored, for example, in a storage medium such as an electronicallyerasable programmable read only memory (EEPROM), flash memory, register,etc.

It is to be understood that the mismatch estimating & compensating unit200 may be implemented in the same chip as, for example, theup-converter 10 of FIG. 1. Alternately, the mismatch estimating &compensating unit 200 may be implemented in a separate chip as theup-converter 10.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it should be understoodby those of ordinary skill in the art that various changes,substitutions and alterations can be made herein without departing fromthe scope of the invention as defined by appended claims and theirequivalents.

1. A device for estimating a mismatch of a transmitter comprising anup-converter, the device comprising: a mismatch compensating unit forreceiving a first in-phase signal and a first quadrature-phase signal togenerate a mismatch compensation signal using a mismatch compensationvalue; a down-converter for mixing a radio frequency (RF) signal with anoscillating signal to generate a second in-phase signal and a secondquadrature-phase signal, wherein an up-converter generates the RF signalusing the mismatch compensation signal; a first square unit for squaringthe second in-phase signal; a second square unit for squaring the secondquadrature-phase signal; a first adder for adding an output of the firstsquare unit to an output of the second square unit; and a low passfilter for filtering an output of the first adder to generate anestimated mismatch value.
 2. The device of claim 1, wherein the mismatchcompensation value is determined to minimize the estimated mismatchvalue.
 3. The device of claim 1, wherein the up-converter is a directup-converter.
 4. The device of claim 1, wherein the mismatchcompensating unit comprises: a phase shifting unit for shifting a phaseof the first quadrature-phase signal based on the mismatch compensationvalue; a second adder for adding the first in-phase signal to a thirdquadrature-phase signal, wherein the third quadrature-phase signalcomprises a lead phase with respect to the first quadrature-phasesignal; a subtractor for subtracting the first in-phase signal from afourth quadrature-phase signal, wherein the fourth quadrature-phasesignal comprises a delay phase with respect to the firstquadrature-phase signal; and an amplifier for amplifying an output ofthe subtractor, wherein a gain of the amplifier varies based on themismatch compensation value.
 5. The device of claim 1, wherein thedown-converter comprises: a first local oscillator for generating afirst oscillating signal; a first mixer for mixing the RF signal withthe first oscillating signal to generate an intermediate frequency (IF)signal; a second low pass filter for filtering an output of the firstmixer; a second local oscillator for generating a second oscillatingsignal; and a second mixer for mixing an output of the second low passfilter with the second oscillating signal to generate a second in-phasesignal and a second quadrature-phase signal.
 6. A method of compensatingfor a mismatch of a transmitter comprising a direct up-converter, themethod comprising: adjusting a phase and a gain of a first in-phasesignal and a first quadrature-phase signal using a first mismatchcompensation value to generate a mismatch compensation signal;up-converting the mismatch compensation signal to generate a radiofrequency (RF) signal; down-converting the RF signal to generate asecond in-phase signal and a second quadrature-phase signal; squaringthe second in-phase signal and the second quadrature-phase signal, toadd the squared second in-phase signal to the squared secondquadrature-phase, and to generate an estimated mismatch value; andgenerating a second mismatch compensation value to compensate for amismatch of a transmitter using the second mismatch compensation value.7. The method of claim 6, wherein the second mismatch compensating valueis determined to minimize the estimated mismatch value.
 8. The method ofclaim 6, wherein the step of adjusting the phase and the gain of thefirst in-phase signal and the first quadrature-phase signal, furthercomprises: shifting the phase of the first in-phase signal and the phaseof the first quadrature-phase signal to adjust the gain of the firstin-phase signal and the gain of the first quadrature-phase signal basedon the mismatch compensation value.
 9. The method of claim 6, whereinthe second mismatch compensation value is stored in a memory tocompensate for the mismatch of the transmitter.
 10. A method ofcompensating for a mismatch of an up-converter, the method comprising:(i) compensating for an input signal using a first mismatch compensationvalue to generate a mismatch compensation signal; (ii) up-converting themismatch compensation signal to generate a radio frequency (RF) signal;(iii) down-converting the RF signal to generate an intermediatefrequency (IF) signal; (iv) squaring the IF signal; and repeating steps(i-iv) to determine a second mismatch compensation value such that adirect current (DC) component of the squared IF signal has a minimumvalue, and to compensate for the mismatch of the up-converter using thesecond mismatch compensation value.
 11. The method of claim 10, whereinthe first mismatch compensation value is changed when repeating steps(i-iv) to determine the second mismatch compensation value.
 12. Themethod of claim 10, wherein the first mismatch compensation valuecomprises one of a phase value and a gain value.
 13. The method of claim12, wherein the input signal comprises a first in-phase signal and afirst quadrature-phase signal, wherein the step of generating themismatch compensation signal comprises: shifting a phase value of thefirst quadrature-phase signal based on a phase value of the firstmismatch compensation value to generate a third quadrature-phase signalhaving a lead phase with respect to the first quadrature-phase signal;shifting the phase of the first quadrature-phase signal based on thephase value of the first mismatch compensation value to generate afourth quadrature-phase signal having a delay phase with respect to thefirst quadrature-phase signal; adding the first in-phase signal to thethird quadrature-phase signal to generate a first mismatch compensationsignal; and obtaining a difference between the first in-phase signal andthe fourth quadrature-phase signal to generate a second mismatchcompensation signal.
 14. The method of claim 13, wherein the step ofgenerating the mismatch compensation signal further comprises:amplifying the second mismatch compensation signal using the gain valueof the first mismatch compensation value.
 15. A device for compensatingfor a mismatch of an up-converter, the device comprising: a mismatchcompensating unit for compensating for an input signal using a firstmismatch compensation value to generate a mismatch compensation signal;a down-converter for down-converting a radio frequency (RF) signal togenerate an intermediate frequency (IF) signal, the RF signal beinggenerated by up-converting the mismatch compensation signal; a squareunit for squaring the IF signal; and a controller for calibrating thefirst mismatch compensation value to determine a second mismatchcompensation value such that a direct current (DC) component of thesquared IF signal has a minimum value to compensate for the mismatch ofthe up-converter using the second mismatch compensation value.
 16. Thedevice of claim 15, wherein the first mismatch compensation valuecomprises a phase value or a gain value.
 17. The device of claim 16,wherein the input signal comprises a first in-phase signal and a firstquadrature-phase signal, wherein the mismatch compensating unitcomprises: a first phase shifter for shifting a phase of the firstquadrature-phase signal based on the phase value of the first mismatchcompensation value to generate a third quadrature-phase signal having alead phase with respect to the first quadrature-phase signal; a secondphase shifter for shifting the phase of the first quadrature-phasesignal based on the phase value of the first mismatch compensation valueto generate a fourth quadrature-phase signal having a delay phase withrespect to the first quadrature-phase signal; a first adder for addingthe first in-phase signal to the third quadrature-phase signal togenerate a first mismatch compensation signal; and a subtractor forobtaining a difference between the first in-phase signal and the fourthquadrature-phase signal to generate a second mismatch compensationsignal.
 18. The device of claim 17, wherein the device furthercomprises: an amplifier for amplifying the second mismatch compensationsignal using the gain value of the first mismatch compensation value.19. The device of claim 17, wherein the down-converter comprises: afirst mixer for mixing the RF signal with a first oscillating signal togenerate a first IF signal; a first low pass filter for filtering thefirst IF signal; and a second mixer for mixing an output of the firstlow pass filter with a second oscillating signal to generate a pair ofsecond IF signals.
 20. The device of claim 19, wherein the square unitcomprises: a first square unit for squaring one of the second IFsignals; a second square unit for squaring one of the second IF signals;a second adder for adding an output of the first square unit to anoutput of the second square unit; and a second low pass filter forfiltering an output of the first adder to extract a DC component fromthe output of the first adder.